Many systems, such as home entertainment systems including set top boxes and the like, are designed with low power codecs. Usual codec voltages range from 1.8V to 3.3V, in these circumstances the maximum audio swing available at the typical DAC output is about 1 VRMS. In order to increase the signal-to-noise ratio (SNR), system designers often drive this DAC output through an operational amplifier with a programmed gain. The amplifier will provide an output voltage swing of greater than 3VRMS which is considered good enough for a signal-to-noise ratio of more than 48 dB. In order to amplify this signal to 3VRMS, the operational amplifier has to run at a single ended supply greater than 9V.
The systems therefore typically include a DC-blocking or coupling capacitor at the output stage of the operational amplifier; this blocking capacitor causes an audible noise to form during startup and shutdown of the system. This noise is known as pop-noise.